Title: #2308: Delete empty keytab during client installation
Client installation fails if '/etc/krb5.keytab' exists as a zero-length file.
Deleting empty keytab before proceeding with the installation fixes the problem.
Signed-off-by: Armando Neto <abiagion(a)redhat.com>
**Note to reviewers:**
Function implemented instead of an in-place solution, so it could be easily tested, if
this solution is overkill I don't mind to remove the test case and move the
check-and-delete procedure to where the function is being called.
To pull the PR as Git branch:
git remote add ghfreeipa https://github.com/freeipa/freeipa
git fetch ghfreeipa pull/2308/head:pr2308
git checkout pr2308